Spread illuminating apparatus

ABSTRACT

There is provided a spread illuminating apparatus aiming to minimize the coverage of a liquid crystal screen while securely integrating a light conductive member with a transparent substrate. The light conductive member is wedge-shaped in which the width thereof is in inverse proportion to the increase in distance from a spot-like light source opposing face, and the transparent substrate is trapezoid-shaped in which a side aligned to the spot-like light source opposing face is shorter. A frame and transparent substrate overlapping part becomes larger from one side part to the other side part of the transparent substrate. Since the frame and transparent substrate overlapping part are large enough regardless of the small width of the frame than that of the prior art, the region of a liquid crystal screen can be increased accordingly.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a spread illuminating apparatus,and more particularly to the spread illuminating apparatus used as anilluminating means for a liquid crystal display device.

[0003] 2. Description of the Related Art

[0004] A demand for a liquid crystal display device operating in a lowpower consumption is increasing mainly for personal computers orportable telephones due to its low profile and light weight. Since aliquid crystal of the liquid crystal display device does not emit lightby itself unlike a light emitting element such as a cathode-ray tube, aseparate illuminating means is required besides the liquid crystaldisplay device when observing images. In particular, a spreadilluminating apparatus of side light type (light conductive plate type)is used as an illuminating means for the liquid crystal display deviceso as to satisfy the recent demand for the low profile as well as energysaving.

[0005]FIG. 4 shows an example of such a spread illuminating apparatus ofside light type.

[0006] In FIG. 4, a spread illuminating apparatus 1, which includes arectangular transparent substrate made of a light transmissiblematerial, generally comprises a bar-like light source 4 disposed alongone end face 3 of a transparent substrate 2 made of alight-transmissible material. The transparent substrate 2 formed into aplate-like rectangle has a light reflection pattern 5 on a surface (anupper side in FIG. 4).

[0007] The light source 4 is generally composed of a bar-like lightconductive member 6 made of a transparent material and disposed close toand along the one end face 3 of the transparent substrate 2, and aspot-like light source 7 disposed on one end face of the lightconductive member 6.

[0008] An optical path conversion means 8 is provided on the lightconductive member 6. The optical path conversion means 8 comprises aplurality of grooves 9 which are, for example, triangular in section,and extended in the thickness direction (the vertical direction in FIG.4) of the light conductive member 6, and formed in the longitudinaldirection of the light conductive member 6 on a face 6 b opposite to atransparent substrate opposing face 6 a, and light emitted from thespot-like light source 7 is incident on the one end face 3 of thetransparent substrate 2 in a substantially uniform manner. The depth ofthe grooves 9 triangular in section is in proportion to the increase indistance from the spot-like light source 7 being able to unify thelight.

[0009] In order to improve the light utilization efficiency of the lightconductive member 6, a frame 10 which is substantially U-shaped insection and has a light reflection member (not shown) inside thereofcovers a surface of the light conductive member 6 except the transparentsubstrate opposing face 6 a and also covers a proximal portion (a parton the end face 3 side) of the transparent substrate 2 thus collectinglight beams leaked from the light conductive member 6.

[0010] In addition, the frame 10 also works not to detach the lightconductive member 6 from the transparent substrate 2 with a specifiedstrength. In order to reliably integrate the light conductive member 6with the transparent substrate 2, the width L1 of the frame 10 is widerat least by 1 to 3 mm than the width L2 of the light conductive member 6thereby covering the proximal portion of the transparent substrate 2.Accordingly, in the spread illuminating apparatus 1 in FIG. 4, the widthL1 of the frame 10 is set to be 4 to 6 mm while the width L2 of thelight conductive member 6 is 3 mm.

[0011] In the spread illuminating apparatus described above, the marketthereof demands for obtaining a larger size of the liquid crystal screenas possible. Meeting the above demand, the frame covering portion overthe liquid crystal screen should be as small as possible to thecontrary. Thus, the reduction of the width L1 for the frame 10 will beone of the options to achieve the larger liquid crystal screen.

[0012] However, if the width L1 of the frame 10 is reduced as describedabove, the portion of the frame 10 overlapped with the transparentsubstrate 2 is reduced accordingly, whereby the required strength forintegrating the light conductive member 6 with the transparent substrate2 will be insufficient and not satisfy the recent demand.

SUMMARY OF THE INVENTION

[0013] The present invention has been made in light of the aboveproblems, and the object thereof is to provide a spread illuminatingapparatus in which a portion covering a liquid crystal screen is reducedto a minimum while surely integrating a light conductive member with thetransparent substrate.

[0014] In order to solve the above problems, according to a first aspectof the present invention, there is provided a spread illuminatingapparatus including a rectangular transparent substrate made of a lighttransmissible material, in which a bar-like light source comprising abar-like light conductive member made of a transparent material and aspot-like light source disposed on one end face of the light conductivemember is disposed along one end face of the rectangular transparentsubstrate and a frame is held on the transparent substrate so as tocover the light conductive member, wherein the light conductive memberis wedge-shaped such that a width of one end thereof facing a spot-likelight source is larger than a width of the other end opposite the oneend; and the transparent substrate is structured such that one endthereof facing the light conductive member is inclined and has aninclination angle forming an obtuse angle with respect to one sidethereof aligned to the one end of the light conductive member facing thespot-like light source.

[0015] According to a second aspect of the present invention, in thespread illuminating apparatus according to the first aspect of thepresent invention, the inclination angle of the transparent substrate isset to be substantially supplementary to the light conductive memberinclination angle which is formed by one side of the light conductivemember facing the transparent substrate with respect to the one end facefacing the spot-like light source.

[0016] According to a third aspect of the present invention, in thespread illuminating apparatus according to the first or second aspect ofthe present invention, one light source is provided, and wherein thetransparent substrate is trapezoid-shaped such that one side thereofaligned to the one end of the light conductive member facing thespot-like light source is shorter than the other side opposite to theone side.

[0017] According to a fourth aspect of the present invention, in thespread illuminating apparatus according to the first or second aspect ofthe present invention, two light sources are provided, and each of thetwo light sources is disposed along each of both ends of the transparentsubstrate opposite to each other.

[0018] According to a fifth aspect of the present invention, in thespread illuminating apparatus according to the fourth aspect of thepresent invention, respective one ends of respective light conductivemembers of the two light sources, which face respective spot-like lightsources, are located to be aligned to one same side of the transparentsubstrate, and the transparent substrate is trapezoid-shaped.

[0019] According to a sixth aspect of the present invention, in thespread illuminating apparatus according to the fourth aspect of thepresent invention, respective one ends of respective light conductivemembers of the two light sources, which face respective spot-like lightsources, are located to be aligned to respective sides of saidtransparent substrate opposite to each other, and the transparentsubstrate is parallelogram-shaped.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is an exploded perspective view of a spread illuminatingapparatus according to an embodiment of the present invention;

[0021]FIG. 2 is a schematic plan view of a spread illuminating apparatushaving two light sources with a trapezoidal transparent substrate;

[0022]FIG. 3 is a schematic plan view of a spread illuminating apparatushaving two light sources with a parallelogram transparent substrate; and

[0023]FIG. 4 is an exploded perspective view of an example of aconventional spread illuminating apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] A preferred embodiment of the present invention for anilluminating apparatus 1A will be hereinafter described with referenceto FIG. 1. The components identical with or corresponding to those inFIG. 4 are represented by the same reference numerals, and detaileddescription thereof is omitted.

[0025] This spread illuminating apparatus 1A generally comprises asubstantially trapezoidal transparent substrate 20 made of alight-transmissible material, a bar-like light source 4A disposed closeto one end face 20 a of the transparent substrate 20, and a frame 10Asubstantially U-shaped in its section which is formed of a metal such asstainless steel, of specified wall thickness and has appropriaterigidity and spring property as illustrated in FIG. 1, and is disposedso as to cover an observation surface of a reflection type liquidcrystal device (not shown) and used as its auxiliary illumination.

[0026] The light source 4A generally comprises a wedge-like and bar-like(long square prismatic) light conductive member 60 made of a transparentmaterial, and a spot-like light source 7 comprising a light emittingdiode disposed on the one end face of the light conductive member 60(hereinafter, referred to as the “spot-like light source opposing face”)60 c. The spot-like light source 7 is mounted on a Flexible PrintedCircuit (FPC) 11.

[0027] The light conductive member 60 is wedge-shaped, and the widththereof is in inverse proportion to the increase in distance from thespot-like light source opposing face 60 c. This means that the lightconductive member 60 is wedge-shaped in which the side of the spot-likelight source opposing face 60 c is the thickest. In the presentembodiment, the width L2 of the spot-like light source opposing face 60c (the side on which the spot-like light source 7 is disposed) of thelight conductive member 60 is set to 3 mm, while the width L3 of a faceopposite to the spot-like light source opposing face 60 c of the lightconductive member 60 is set to 0.1 to 1.0 mm. A face (a transparentsubstrate opposing face) 60 a opposing the transparent substrate 20 anda face 60 b opposite to the transparent substrate opposing face 60 a maybe orthogonal to the spot-like light source opposing face 60 c, or theangle formed by the transparent substrate opposing face 60 a and thespot-like light source opposing face 60 c (hereinafter, referred to asthe light conductive member inclination angle) may form an acute anglewith a prescribed value.

[0028] An optical path conversion means 8 comprising a large number ofgrooves 9 substantially triangular in section and formed in thelongitudinal direction of the light conductive member 60 is provided onthe face 60 b opposite to the transparent substrate opposing face 60 aof the light conductive member 60 in such a manner that light emittedfrom the spot-like light source 7 uniformly enters the one end face 20 aof the transparent substrate 20.

[0029] The transparent substrate 20 is formed in a trapezoid in whichone side 20 c aligned to the spot-like light source opposing face 60 cis shorter than an other side 20 d opposite to the one side 20 c.

[0030] A light reflection pattern 5A is formed on a surface of thetransparent substrate 20 (an upper side in FIG. 1). The light reflectionpattern 5A comprises a large number of grooves 12 and flat portions 13formed therebetween. The grooves 12 substantially triangular in sectionare extended parallel to the optical axis of the bar-like light source4A (orthogonal to the side part 20 c), and a large number of grooves areformed from the one end face 20 a of the transparent substrate 20 to another face 20 b opposite to the one end face 20 a. The grooves 12 areset to be deeper from the one end face 20 a to the other face 20 b ofthe transparent substrate 20.

[0031] The angle formed by the one end face 20 a and the one side 20 cof the transparent substrate 20 (hereinafter referred to as thetransparent substrate inclination angle β) is set to be an obtuse angle.Thus, when the light conductive member 60 is abutted onto thetransparent substrate 20 in such a manner that the one end face 20 a ofthe transparent substrate 20 faces the transparent substrate opposingface 60 a, the whole shape comprising the substantially trapezoidaltransparent substrate 20 and the wedge-shaped light conductive member 60fitted to each other becomes substantially rectangular.

[0032] The frame 10A generally comprises a frame body part 14 oppositeto the one end face 20 a of the transparent substrate 20 with the lightconductive member 60 therebetween, and two plates which are continuousto and substantially orthogonal to the frame body part 14 and disposedopposite to each other so as to hold a part on the one end face 20 aside of the transparent substrate 20 (the upper and lower plates in FIG.1 are hereinafter referred to as an upper opposing plate 15 and a loweropposing plate 16, respectively). A notch 17 is formed in an end part onthe spot-like light source 7 side on the lower opposing plate 16 of theframe 10A so that the spot-like light source 7 can be disposed. Thewidth L1 of the frame 10A is set to 3.5 mm.

[0033] A light reflection member (not shown) is provided on the framebody part 14 of the frame 10A, the upper opposing plate 15, and thelower opposing plate 16 so as to collect leaked light. The frame 10A isformed of a metal, excellent in machinability, and appropriate inrigidity and spring property.

[0034] In the transparent substrate 20 and the light conductive member60, the one end face 20 a and the transparent substrate opposing face 60a are abutted on each other, and the frame 10A is held into a proximalportion (a part on the side of the one end face 20 a) of the transparentsubstrate 20 so as to cover the light conductive member 60 in such amanner that the whole shape of the substantially trapezoidal transparentsubstrate 20 and the wedge-shaped light conductive member 60 are fittedto substantially form a rectangular. The frame 10A has both rigidity andspring property as described above, and thus, the transparent substrate20 is integrated with the light conductive member 60 thereby.

[0035] The light conductive member 60 is integrated with the transparentsubstrate 20 by means of the frame 10A in such a manner as to extend theframe 10A (the upper opposing plate 15 and the lower opposing plate 16)toward the transparent substrate 20 to overlapping. And, the integrationbecomes more secure the more an overlapping part (an overlapping part ofthe frame 10A and the transparent substrate 20) 18 extends over thetransparent substrate 20.

[0036] As described above, in the light conductive member 60, aspot-like light source opposing face 60C facing the spot-like lightsource is wedge-shaped such that a width of one end face thereof islarger than a width of the other end opposite the one end, and thetransparent substrate 20 has a transparent substrate inclination angle βin which the one end face 20 a opposing the light conductive member 60is inclined and has an inclination angle forming an obtuse angle withrespect to one side 20 c of the transparent substrate 20. Thus, when thelight conductive member 60 is abutted on the transparent substrate 20, apart on the other side part 20 d side is brought closer to the countertransparent substrate opposing face 60 b (i.e., a surface part opposingthe frame body part 14 when the frame 10A is assembled) of the lightconductive member 60 than a part on one side part 20 c side with respectto a part on the one end face 20 a side of the transparent substrate 20,whereby the frame and transparent substrate overlapping part 18 can bewidely secured irrespective of the spot-like light source opposing face60C side formed into the thick wedge-shaped. Accordingly, the integratedstrength of the light conductive member 60 with the transparentsubstrate 20 can be increased by means of the frame 10A.

[0037] In the present embodiment, the width L1 of the frame 10A is setto be 3.5 mm, the width L2 of the spot-like light source opposing face60 c of the light conductive member 60 is set to be 3 mm, and the widthL3 of the face opposite to the spot-like light source opposing face 60 cof the light conductive member 60 is set to be 0.1 to 0.8 mm. Thus, whenthe frame 10A is held with the light conductive member 60 abutted on thetransparent substrate 20, the frame and transparent substrateoverlapping part 18 can sufficiently extend toward the transparentsubstrate 20 so that the light conductive member 60 and the transparentsubstrate 20 can be securely integrated with the frame 10A.

[0038] In case the light conductive member inclination angle of thelight conductive member 60 has a supplementary relation to thetransparent substrate inclination angle β of the transparent substrate20, the frame and transparent substrate overlapping part 18 are formedinto a longitudinal trapezoid which becomes wider from one side part 20c to the other side part 20 d on condition that the light conductivemember 60 is abutted to the transparent substrate 20. Accordingly, theframe as a whole becomes wider enough sufficiently obtaining thestrength to integrate the light conductive member 60 with thetransparent substrate 20.

[0039] As described above, in the spread illuminating apparatus 1A, thewidth L1 of the frame 10A is set to be 3.5 mm shorter than theaforementioned prior art (the width L1 is 4 to 6 mm), and thus, theso-called frame covering the liquid crystal screen is narrower resultingin wider liquid crystal screen.

[0040] As described, the present invention has the shorter width L1compared to the prior art; however, sufficiently large area of the frameand transparent substrate overlapping part 18 can be obtained asdescribed above, whereby the strength for integrating the lightconductive member 60 with the transparent substrate 20 can be ensured.

[0041] In the present embodiment, the width L1 of the frame 10A is setto be larger (3.5 mm) than the width L2 (3 mm) of the spot-like lightsource opposing face 60 c; however, the present invention is not limitedthereto. For example, the width L1 of the frame 10A may be set to beequal to the width L2 (3 mm) of the spot-like light source opposing face60 c (L1=3 mm) or the dimension exceeding this value (3 mm<L1<3.5 mm),or may be a value exceeding 3.5 mm (3.5 mm<L1). Further, the width L1 ofthe frame 10A may be set to the value below 3 mm if the strength forintegrating the light conductive member 60 with the transparentsubstrate 20 is ensured.

[0042] And, the area of the liquid crystal screen can be increasedcompared with the above embodiment by setting the width L1 of the frame10A to be the dimension below 3.5 mm.

[0043] Further, in the above-described embodiment, the width L2 of thespot-like light source opposing face 60 c and the width L3 of the faceopposite thereto are set to be the above-described dimensions (L2=3 mm,and L3=0.1 to 1.0 mm); however, the present invention is not limitedthereto. When the value of the width L2 is changed from theabove-described value (L2=3 mm), the width L1 of the frame 10A ispreferably changed to the value equivalent to or larger than the widthL2 accordingly.

[0044] In the above embodiment, the light conductive member inclinationangle of the light conductive member 60 has a supplementary relation tothe transparent substrate inclination angle β of the transparentsubstrate 20; however, the present invention is not limited thereto, andboth angles may be set to be substantially supplementary to each other.This is applicable to examples shown in FIGS. 2 or 3 as described below.

[0045] Further, in the above-described first embodiment, the lightconductive member inclination angle of the light conductive member 60 isset to have an acute angle; however, the present invention is notlimited thereto, and the inclination angle may be set to be a rightangle or an obtuse angle. This is applicable to examples shown in FIGS.2 or 3 as described hereinafter.

[0046] Further, in the above-described embodiment, a case where thelight conductive member 60 is disposed along the one end face 20 a ofthe transparent substrate 20; however, the light conductive member 60may be respectively disposed on the end faces 20 a and 20 b of thetransparent substrate 20.

[0047] In this case, as shown in FIG. 2, the spot-like light sourceopposing faces 60 c of two light conductive members 60 may be disposedon one side part 20 c side by forming the transparent substrate 20 intotrapezoid.

[0048] Further, as shown in FIG. 3, one spot-like light source opposingface 60 c (an upper side in FIG. 3) of two light conductive members 60may be disposed on one side part 20 c side, and the other spot-likelight source opposing face 60 c (a lower side in FIG. 3) may be disposedon the other side part 20 d side (in this example, the one side part 20c and the other side part 20 d constitute the side parts opposite toeach other of the transparent substrate) by forming the transparentsubstrate 20 into parallelogram.

[0049] In the above-described embodiment, the spot-like light source 7uses a light emitting diode; however, the present invention is notlimited thereto, and, for example, the spot-like light source may be anincandescent lamp which can be lit at relatively low voltage.

[0050] In the above-described embodiment, a case where the grooves 9 ofthe optical path conversion means 8 and the grooves 12 of the lightreflection pattern 5A are substantially triangular in section; however,the present invention is not limited thereto, and the grooves may besubstantially trapezoidal or stepped in section.

[0051] According to the present invention, the light conductive memberis wedge-shaped such that a width of the spot-like light source opposingface side is larger than a width of the other end side, and in thetransparent substrate, the one end face facing the light conductivemember is inclined and has an inclination angle forming the obtuse anglewith respect to the side aligned to the spot-like light source opposingface, and thus, when the light conductive member is abutted on thetransparent substrate, the one end face of the transparent substratecorresponding to the L3 side of the light conductive member is madecloser to the face opposite to the transparent substrate opposing faceof the light conductive member than the one end face of the transparentsubstrate corresponding to the L2 side. Therefore, the part of the frameoverlapping the transparent substrate can be increased irrespective ofthat the light conductive member has the spot-like light source opposingface side being thicker so as to improve the strength for integratingthe light conductive member with the transparent substrate by the framethus constructed.

[0052] By making the transparent substrate inclination anglesubstantially supplementary to the light conductive member inclinationangle, the frame and transparent substrate overlapping part are formedinto a longitudinal triangle or trapezoid shape becoming wider from oneside part to the other of the transparent substrate when the lightconductive member is abutted on the transparent substrate. And, thewidth of the frame will be wide enough to obtain the strengthintegrating the light conductive member with the transparent substrate.

[0053] In addition, even when the width of the frame is reduced comparedwith that of the prior art, the overlapping part is still large enough,and, at the same time, the so-called frame covering the liquid crystalscreen is reduced due to the reduction of the width of the frame so asto provide the wider liquid crystal screen.

What is claimed is:
 1. A spread illuminating apparatus, which includes arectangular transparent substrate made of a light transmissiblematerial, a bar-like light source comprising a bar-like light conductivemember made of a transparent material and a spot-like light sourcedisposed on one end face of said light conductive member, and disposedalong one end face of said transparent substrate, and which includes aframe held on said transparent substrate so as to cover said lightconductive member, wherein said light conductive member is wedge-shapedsuch that a width of one end thereof facing said spot-like light sourceis larger than a width of the other end opposite said one end, andwherein said transparent substrate is structured such that one endthereof facing said light conductive member is inclined and has aninclination angle forming an obtuse angle with respect to one sidethereof aligned to said one end of said light conductive member facingsaid spot-like light source.
 2. A spread illuminating apparatusaccording to claim 1, wherein said inclination angle of said transparentsubstrate is set to be substantially supplementary to a light conductivemember inclination angle which is formed by one side of said lightconductive member facing said transparent substrate with respect to saidone end thereof facing said spot-like light source.
 3. A spreadilluminating apparatus according to claim 1 or 2, wherein one lightsource is provided, and wherein said transparent substrate istrapezoid-shaped such that said one side thereof aligned to said one endof said light conductive member facing said spot-like light source isshorter than the other side opposite to said one side.
 4. A spreadilluminating apparatus according to claim 1 or 2, wherein two lightsources are provided, and wherein each of said two light sources isdisposed along each of both ends of said transparent substrate oppositeto each other.
 5. A spread illuminating apparatus according to claim 4,wherein respective one ends of respective light conductive members ofsaid two light sources, which face respective spot-like light sources,are located to be aligned to one same side of said transparentsubstrate, and wherein said transparent substrate is trapezoid-shaped.6. A spread illuminating apparatus according to claim 4, whereinrespective one ends of respective light conductive members of said twolight sources, which face respective spot-like light sources, arelocated to be aligned to respective sides of said transparent substrateopposite to each other, and wherein said transparent substrate isparallelogram-shaped.